Command failed due to signal: Segmentation fault: 11 while emitting IR SIL function

Question

I want to add closure properties in the extension of UITextView so I define a closure using typealias:

typealias TextViewHeightDidChangedClosure = (_ currentTextViewHeight:CGFloat)->Void

extension UITextView{

  func setTextViewHeightDidChanged(textViewHeightDidChanged:TextViewHeightDidChangedBlock){
    objc_setAssociatedObject(self, &TextViewHeightDidChangedBlockKey, textViewHeightDidChanged, objc_AssociationPolicy.OBJC_ASSOCIATION_COPY_NONATOMIC)
  }

  func textViewHeightDidChanged()->TextViewHeightDidChangedBlock?{
   let textChanged : ((CGFloat)->Void) = objc_getAssociatedObject(self, &TextViewHeightDidChangedBlockKey) as! TextViewHeightDidChangedBlock
    return textChanged
  }

}

But it tells me an error that says:

Command failed due to signal: Segmentation fault: 11.

Here is an image of the error

Can anyone tell me why and give me an deep meaningful explanation, thank you very much!

Answer 1

For me it was because I was declaring protocols for two extensions on a generic class and implementing them in the class declaration. I am using xCode 9 swift 4

Answer 2

Generally, crashing with SegFault 11 is a bug of compiler and you'd better send a bug report.

And most such bugs can be worked around with fixing your code properly.

The most significantly bad thing in your code is that usual closures in Swift (@convention(swift) -- usually omitted) cannot be passed to Any which represents id of Objective-C. Use @convention(block) which is stated as id-compatible in the Swift book (this part):

typealias TextViewHeightDidChangedBlock = @convention(block) (_ currentTextViewHeight:CGFloat)->Void

You may have tried this, but in this case, just putting @convention(block) does not solve the issue.

It seems another trick is needed to make your code work, explicitly cast to AnyObject:

extension UITextView{

    func setTextViewHeightDidChanged(textViewHeightDidChanged: @escaping TextViewHeightDidChangedBlock){
        objc_setAssociatedObject(self, &TextViewHeightDidChangedBlockKey, textViewHeightDidChanged as! AnyObject, objc_AssociationPolicy.OBJC_ASSOCIATION_COPY_NONATOMIC)
    }

    func textViewHeightDidChanged()->TextViewHeightDidChangedBlock?{
        let textChanged : ((CGFloat)->Void) = objc_getAssociatedObject(self, &TextViewHeightDidChangedBlockKey) as! TextViewHeightDidChangedBlock
        return textChanged
    }

}

So, this seems to be a flaw of id-as-Any. Any which represents id should accept id-compatible closure.

I'm not sure Apple would fix this bug soon, but anyway, as far as I tested, my code above worked as expected.

Answer 3

You can also have this error if you declare a Bool! property in a class and you try to make a ternary condition with this property:

var isSomething: Bool!

func myFunc() {
    let value = isSomething ? "something" : "not"
}

Just add the ! on your property

var isSomething: Bool!

func myFunc() {
    let value = isSomething! ? "something" : "not"
}